1. Field of the Invention
The present invention relates to an optical interferometer which is used, for example, in an optical measurement technical field.
2. Description of the Related Art
FIG. 13 is a plan view showing an example of a schematic construction of a small-sized optical interferometer according to an earlier development. In this figure, reference numeral 11 denotes an incident light, 12 denotes a beam splitter, 13 and 14 denote mirrors and 15 denotes a photo-detector.
As shown in FIG. 13, the small-sized optical interferometer divides the incident light into two optical paths for a transmitted light and a reflected light, which are perpendicular to each other, by using the beam splitter 12. Two lights reflected on the mirrors 13 and 14 which are disposed so as to be perpendicular to each optical path are multiplexed by the beam splitter 12 again.
At the same time, a direct acting stage (not shown in the figure), on which one mirror 13 is mounted is moved at a constant speed. The optical path difference between the two lights reflected on the mirrors 13 and 14 is caused. A variety of intensity of interference fringes can be observed.
The variety of intensity of interference fringes is fetched by the photo-detector 15 as an electric signal.
Because the mirror 13 is moved along the optical path as described above, the mirror 13 moves a long distance. It takes longer to move the mirror 13. The accuracy of the optical interferometer must be obtained according to the length of the movement.
Therefore, there are limits of the downsizing of the optical interferometer and of the shortening of the measurement time. It is desired to improve a control of the accuracy of the optical interferometer.
However, in case of the small-sized optical interferometer shown in FIG. 13, if the direct acting stage on which the mirror 13 is mounted is not incorporated into a casing which is provided in order to fix the other optical parts thereto, the mechanical adjustment and the optical adjustment cannot be carried out.
Therefore, in a small-sized optical adjustment according to an earlier development, in order to carry out the mechanical adjustment and the optical adjustment, the casing has a certain size. It is desired to improve the downsizing of the optical interferometer. Further, it is desired to improve the optical interferometer so as to obtain many regions in which the optical path difference is caused.
A moving member, such as a direct acting stage, is a consumable part. Because the moving member is approximately united with the casing like an earlier development, good maintenance of the optical interferometer, such as a repair of the moving member or the exchange thereof, cannot be carried out.
Because the moving member is approximately united with the casing as described above, it is necessary to carry out the optical adjustment in the small casing. It is difficult to improve the accuracy of the ratio of the optical interference.
On the other hand, in the Michelson interferometer, a movable mirror can be moved on the same axis as a reference light.
The wavelength of a light can be measured more precisely by moving the movable mirror straight and a long distance.
However, in an optical interferometer according to an earlier development, there is a following problem.
That is, in case of an optical interferometer like the Michelson interferometer in which a movable mirror is moved on the same axis as a reference light, or like the optical interferometer shown in FIG. 13, in which the movable mirror is moved on an axis which is perpendicular to the reference light, in order to move the movable mirror straightly and a long distance, the casing for incorporating each type of optical parts thereinto becomes larger.
In order to solve the above-described problems, an object of the present invention is to provide an optical interferometer which can carry out the mechanical adjustment and the optical adjustment and can improve the maintenance of the moving member and the accuracy of the ratio of the optical interference and which can be sufficiently small.
Another object of the present invention is to provide an optical interferometer which can improve the accuracy of the measurement for a wavelength of a light by moving the movable mirror straight and a long distance and which can be sufficiently small.
That is, in accordance with one aspect of the present invention, the optical interferometer;
the plurality of optical parts are separated into a fixed optical part which is fixed to a casing and a movable optical part which is movable with respect to the casing, and
the movable optical part is incorporated into a block which is removable from the casing.
For example, as an optical part, a beam splitter or a reflector is used.
According to the present invention, because the movable optical part is incorporated into a block which is removable from the casing, the fixed optical part can be adjusted in the casing mechanically and optically by removing the block into which the movable optical part is incorporated from the casing. Further, the movable optical part which is incorporated into the block removed from the casing can be adjusted mechanically and optically. The maintenance of the movable optical part which is incorporated into the block removed from the casing, such as a repair of the movable optical part or an exchange thereof, can be carried out easily.
Because the movable optical part can be removed from the casing as a block, the fixed optical part and the movable optical part can be separately adjusted mechanically and optically. The maintenance of the movable optical part can be improved. Because the fixed optical part is adjusted optically in the casing by removing the movable optical part with the block from the casing, the accuracy of the ratio of the optical interference can be improved. Further, the casing can be efficiently small.
In accordance with another aspect of the present invention, the optical interferometer in which a reference light and a light to be measured branch into two optical paths for a transmitted light and a reflected light, which are perpendicular to each other, by a beam splitter, and in which after the reflected light and the transmitted light are reflected on a plurality of reflecting members each other in each optical path, the reflected light and the transmitted light are multiplexed by the beam splitter to receive the multiplexed light by a photo-detector, is one wherein
the plurality of reflecting members are separated into a fixed reflecting member which is fixed to a casing and a movable reflecting member which is movable with respect to the casing, and
the movable reflecting member is incorporated into a block which is removable from the casing.
For example, a representative reflecting member is a mirror. Instead of a mirror, for example, a corner cube or a reflector may be used.
The photo-detector is one for fetching a variety of intensity of interference fringes as an electric signal.
According to the present invention, because the movable reflecting member is incorporated into a block which is removable from the casing, the beam splitter and the fixed reflecting member can be adjusted in the casing mechanically and optically by removing the block into which the movable reflecting member is incorporated from the casing. Further, the movable reflecting member which is incorporated into the block removed from the casing can be adjusted mechanically and optically. The maintenance of the movable reflecting member which is incorporated into the block removed from the casing, such as a repair of the movable reflecting member or an exchange thereof, can be carried out easily.
Because the movable reflecting member can be removed from the casing as a block, the beam splitter and the fixed reflecting member can be adjusted mechanically and optically so that the movable reflecting member is adjusted separately from them. The maintenance of the movable reflecting member can be improved. Because the beam splitter and the fixed reflecting member are adjusted optically in the casing by removing the movable reflecting member with the block from the casing, the accuracy of the ratio of the optical interference can be improved. Further, the casing can be efficiently small.
A pair of fixed reflecting members for reflecting the reflected light and the transmitted light toward the other fixed reflecting member each other may be provided, and a pair of movable reflecting members for totally reflecting a light toward each fixed reflecting member may be disposed between the pair of fixed reflecting members.
According to the present invention, because a pair of movable reflecting members for totally reflecting a light toward each fixed reflecting member is disposed on the block which is removable from the casing between the pair of fixed reflecting members for reflecting the reflected light and the transmitted light toward the other fixed reflecting member each other, when a pair of fixed reflecting members is adjusted in the casing mechanically and optically by removing a pair of movable reflecting members with the block from the casing, the movable reflecting members do not exist between a pair of fixed reflecting members. As a result, a pair of fixed reflecting members can be adjusted more precisely.
A reference surface for adjusting an optical axis so that the reference surface is in parallel with the optical axis may be provided in the casing.
According to the present invention, because the reference surface for adjusting an optical axis so that the reference surface is in parallel with the optical axis is provided in the casing, the optical axis can be adjusted on the basis of the reference surface so that the reference surface is in parallel with the optical axis.
A reference surface for adjusting an optical axis of the movable optical part may be provided in the casing and the block, respectively.
According to the present invention, because the reference surface for adjusting an optical axis of the movable optical parts is provided in the casing and the block, respectively, the optical axis of the movable optical part can be adjusted on the basis of the reference surface which is provided on the block. Further, the block can be precisely disposed in a predetermined position of the casing by fitting the reference surface which is provided on the block to one which is provided in the casing.
In accordance with another aspect of the present invention, the optical interferometer is one wherein the plurality of optical parts are separated into a fixed optical part which is fixed to a casing and a movable optical part which is movable with respect to the casing, and the movable optical part is disposed on an optical axis which is approximately parallel to an optical axis of the reference light.
the plurality of optical parts are separated into a fixed optical part which is fixed to a casing and a movable optical part which is movable with respect to the casing, and
the movable optical part is disposed on an optical axis which is approximately parallel to an optical axis of the reference light.
For example, as an optical part, a beam splitter or a reflector is used.
According to the present invention, because the movable optical part is disposed on an optical axis which is approximately parallel to an optical axis of the reference light, the wavelength of a light can be measured more precisely by moving the movable optical part a long distance along an optical axis which is approximately parallel to the optical axis of the reference light. Further, the casing can be sufficiently small.
In accordance with another aspect of the present invention, the optical interferometer in which a reference light and a light to be measured branch into two optical paths for a transmitted light and a reflected light, which are perpendicular to each other, by a beam splitter, and in which after the reflected light and the transmitted light are reflected on a plurality of reflecting members each other in each optical path, the reflected light and the transmitted light are multiplexed by the beam splitter to receive the multiplexed light by a photo-detector, is one wherein
the plurality of reflecting members are separated into a fixed reflecting member which is fixed to a casing and a movable reflecting member which is movable with respect to the casing, and
the movable reflecting member is disposed on an optical axis which is approximately parallel to an optical axis of the reference light.
For example, a representative reflecting member is a mirror. Instead of a mirror, for example, a corner cube or a reflector may be used.
The photo-detector is one for fetching a variety of intensity of interference fringes as an electric signal.
According to the present invention, because the movable reflecting member is disposed on an optical axis which is approximately parallel to an optical axis of the reference light, the wavelength of a light can be measured more precisely by moving the movable reflecting member a long distance along an optical axis which is approximately parallel to the optical axis of the reference light. Further, the casing can be sufficiently small.
A pair of fixed reflecting members for reflecting the reflected light and the transmitted light toward the other fixed reflecting member each other may be provided, and a pair of movable reflecting members for totally reflecting a light toward each fixed reflecting member may be disposed between the pair of fixed reflecting members.
According to the present invention, because a pair of movable reflecting members for totally reflecting a light toward each fixed reflecting member is disposed between the pair of fixed reflecting members for reflecting the reflected light and the transmitted light toward the other fixed reflecting member each other, a wide range in which an optical path difference between two lights is caused can be obtained by moving the pair of movable reflecting members between the pair of fixed reflecting members on an optical axis which is approximately parallel to the optical axis of the reference light so as to reflect each light totally.
The pair of movable reflecting members may be removable from the casing.
According to the present invention, because the pair of movable reflecting members can be removable from the casing, the pair of fixed reflecting members which is arranged so as to face each other at both end sides of an optical axis which is approximately to the optical axis of the reference light can be adjusted mechanically and optically by removing the pair of movable reflecting members from the casing. Further, an optical axis between the pair of fixed reflecting members can be adjusted more precisely.
By removing the pair of movable reflecting members, the reference light can outgo toward the outside of the casing after the reference light passes between the pair of fixed reflecting members and is reflected on the pair of fixed reflecting members. Therefore, when the reference light outgoes far toward the outside of the casing, the accuracy of the parallel between the optical axis between the pair of fixed reflecting members, and the optical axis of the reference light can be adjusted more precisely.
An attachment base for the movable optical part may be fixed to a driving member on both sides of the movable optical part and on a line crossing a moving direction of the movable optical part.
For example, the typical line which crosses the moving direction is one which is perpendicular to the moving direction. If only the line crosses the moving direction, the effect which is described below can be obtained.
According to the present invention, the attachment base for the movable optical part is fixed to a driving member on both sides of the movable optical part and on the line crossing a moving direction of the movable optical part. Even though the movable optical part is moved as a long distance as possible, because the fixed positions of the attachment base fixed to the driving member for moving the movable optical part are on the both sides and on the line crossing the moving direction of the movable optical part, the moving stroke of the movable optical part can be obtained without causing an obstruction. The attachment base can be attached reasonably.
In accordance with another aspect of the present invention, the optical interferometer is one wherein the plurality of optical parts are separated into a fixed optical part which is fixed to a casing and a movable optical part which is movable with respect to the casing, the movable optical part is disposed on an optical axis which is approximately parallel to an optical axis of the reference light, and an optical path the transmitted light and that of the reflected light are arranged between a driving member for moving the movable optical part along the optical axis which is approximately parallel to the optical axis of the reference light and a guide member therefor.
For example, as an optical part, a beam splitter or a reflector is used.
As a driving member, a timing belt is used. However, the driving member may be a simple belt or a wire.
As a guide member, a linear guide is used. However, the guide member may be any other members which can guide the movable optical part straightly.
According to the present invention, because the movable optical part is disposed on an optical axis which is approximately parallel to an optical axis of the reference light, the wavelength of a light can be measured more precisely by moving the movable optical part a long distance along an optical axis which is approximately parallel to the optical axis of the reference light. Further, the casing can be sufficiently smale.
Because the optical path of the transmitted light and that of the reflected light are arranged between the driving member of the movable optical part and the guide member thereof, the optical interferometer has a reasonable arrangement for the driving member and the guide member, in which the reference light and the light to be measured are not influenced. Therefore, for this reason, the casing can be smaller.
In accordance with another aspect of the present invention, the optical interferometer in which a reference light and a light to be measured branch into two optical paths for a transmitted light and a reflected light, which are perpendicular to each other, by a beam splitter, and in which after the reflected light and the transmitted light are reflected on a plurality of reflecting members each other in each optical path, the reflected light and the transmitted light are multiplexed by the beam splitter to receive the multiplexed light by a photo-detector, is one wherein the plurality of reflecting members are separated into a fixed reflecting member which is fixed to a casing and a movable reflecting member which is movable with respect to the casing, the movable reflecting member is disposed on an optical axis which is approximately parallel to an optical axis of the reference light, and an optical path of the transmitted light and that of the reflected light are arranged between a driving member for moving the movable reflecting member along the optical axis which is approximately parallel to the optical axis of the reference light and a guide member therefore.
For example, a representative reflecting member is a mirror. Instead of a mirror, for example, a corner cube or a reflector may be used.
The photo-detector is one for fetching a variety of intensity of interference fringes as an electric signal.
According to the present invention, because the movable reflecting member is disposed on an optical axis which is approximately parallel to an optical axis of the reference light, the wavelength of a light can be measured more precisely by moving the movable reflecting member a long distance along an optical axis which is approximately parallel to the optical axis of the reference light. Further, the casing can be sufficiently small.
Because the optical path of the reference light and that of the light to be measured are arranged between the driving member of the movable reflecting member and the guide member thereof, the optical interferometer has a reasonable arrangement for the driving member and the guide member, in which the transmitted light and that of the reflected light are not influenced. Therefore, for this reason, the casing can be smaller.
A pair of fixed reflecting members for reflecting the reflected light and the transmitted light toward the other fixed reflecting member each other may be provided, and a pair of movable reflecting members for totally reflecting a light toward each fixed reflecting member may be disposed between the pair of fixed reflecting members.
According to the present invention, because a pair of movable reflecting members for totally reflecting a light toward each fixed reflecting member is disposed between the pair of fixed reflecting members for reflecting the reflected light and the transmitted light toward the other fixed reflecting member each other, a wide range in which an optical path difference between two lights is caused can be obtained by moving the pair of movable reflecting members between the pair of fixed reflecting members on an optical axis which is approximately parallel to the optical axis of the reference light so as to reflect each light totally.
The driving source for driving the driving member may be disposed at an approximate center of the pair of fixed reflecting members.
For example, as a driving source, a stepping motor is used. However, the driving source may be a simple motor or any other driving device.
According to the present invention, because the driving source for driving the driving member is disposed at an approximate center of the pair of fixed reflecting members, the pair of movable reflecting members can be moved along the optical axis in both directions in the same way by driving the driving source which is positioned at the approximate center of a pair of the fixed reflecting members disposed on both sides of the movable reflecting members via the driving member.
An optical axis of the light to be measured and that of an interference light may be arranged so that the optical axis of the light to be measured is approximately perpendicular to that of the interference light, and
the casing may be formed so as to have a shape of a hexagon which comprises two sides which are approximately parallel to the optical axis of the reference light, two sides which are approximately perpendicular to the optical axis of the reference light, one side which is approximately perpendicular to the optical axis of the light to be measured and one side which is approximately perpendicular to the optical axis of the interference light.
According to the present invention, because the casing is formed so as to have a shape of a hexagon which comprises two sides which are approximately parallel to the optical axis of the reference light, two sides which are approximately perpendicular to the reference optical axis, one side which is approximately perpendicular to the optical axis of the light to be measured and one side which is approximately perpendicular to the optical axis of the interference light, which is arranged so that the optical axis of the light to be measured is approximately perpendicular to the optical axis of the interference light, as compared with the casing having a shape of a quadrilateral, two corners of a quadrilateral are chamfered. As a result, the casing can be smaller.
In accordance with another aspect of the present invention, the optical interferometer comprises: a casing, a movable optical part which is movable with respect to the casing, a fixed optical part which is fixed to the casing, and an attachment member for attaching the movable optical part to the casing, and for removing the movable optical part from the casing.
In accordance with another aspect of the present invention, the optical interferometer comprises: a reference light source for outgoing the reference light, a movable optical part which is arranged on an optical axis which is approximately parallel to an optical axis of the reference light and which moves in a direction which is approximately parallel to the optical axis of the reference light, and a fixed optical part for reflecting the reference light and the light to be measured so as to direct the reflected lights to the movable optical part along the direction.
The optical interferometer may further comprises;
a driving member for moving the movable optical part in the direction, and
a guide member for guiding the movable optical part in the direction,
wherein optical axes of the reflected lights are arranged between the driving member and the guide member.